5.1.1 Thermoregularion In Endotherms Flashcards
What do the temp receptors in the hypothalamus act as
A thermostat, maintaining responses within a dynamic equilibrium within about 1°C of 37°C.
What are the principles of thermoregulation in endotherms
They use their internal exothermic metabolic activities to keep them warm, and energy requiring physiological reactions keep them cool. They also have passive ways of heating and cooling, to reduce the energy demands on the body.
Like ectotherms endotherms also have a range of behavioural things to temp change like basking, wallowing in mud or water, digging burrows. Some hibernate.
Humans also have additional behavioural adaptions like clothes, houses…
However unlike ectotherms, endotherms primarily rely on physiological reactions rather than behavioural
How does vasodilation cool ting
Vasodilation - arterioles near surface of the skin dilate when temp rises. And the vessels that provide a direct connection between arterioles and venues constrict. This forces blood through the capillary networks near the skin. The skin flushes and cools as a result of increased radiation. The skin can also be pressed against cool surface in which cooling from conduction occurs.
How does sweating cool ting
As core temp increases so does sweating. Sweat spreads out across the surface of the skin. In some mammals there are sweat glands all over the body and as sweat evaporates from the surface of the skin, heat is lost, cooling the blood below the surface. Some mammals have sweat glands that are not in hairy places, for example paws. These mammals often open their mouth as well and pant in which water evaporates.
What do hairs do to cool down in endothermic
Hair erector muscles on skin relax - hairs lie flat on skin avoiding trapping an insulating layer of air.
How do anatomical adaptions cuh
They increase surface area to volume ratio to maximise cooling, I.e, large hairs or wrinkly skin
How does vasoconstriction work
Arterioles near surface constrict and the arteriovenous shunt vessels dilate, so very little blood flows though the capillary networks close to the surface of the skin. The skin looks pale and very little radiation takes place. Warm blood below surface
What happens to sweating when cold?
Rates of sweating decrease or stop entirely. This greatly reduces cooling by the evaporation of water from the surface of the skin, although some evaporation from the lungs still occur
How do body hairs change to help remain warm
Hair erector muscles contract, making hairs upright, trapping an insulating layer of air and so reduces cooling through the skin. However this has little effect on humans
What does shivering do
As core temp falls we shiver. This is the rapid involuntary contracting and relaxing of the large voluntary muscles in the body. The metabolic heat from the exothermic reactions heat up the body, raising core temp.
Anatomical adaptations to reduce
Small ears to reduce SA:V ratio. Thick layer of insulating fat underneath skin.
Polar bear
- Small ears
- fur on feet
- hollow hairs to trap a permanent layer of insulating air.
- skin underneath is black
- thick layer of fat underneath
What is the heat loss centre
This is activated when the temperature of the blood flowing through the hypothalamus increases. It sends impulses though autonomic motor neurones in the skin and muscles, triggering responses that act to lower the core temperature
What is the heat gain centre?
Activated when blood temp flowing through hypothalamus decreases. Sends impulses through autonomic nervous system to effectors in the skin, triggering responses that act to raise the core temp.
